When grown-ups co-opt a cartoon animal franchise aimed at little girls, everybody wins. Or, in this case, Hasbro and Build-A-Bear Workshop stand to hit it big with a new pair of plush My Little Pony toys that launch Monday.

Sure, elementary-school girls might be excited about the new toys, but men, some old enough to be their dads, are giving them a run for their money. This phenomenon of adults, primarily men (86 percent, according to one online survey), has given the newest iteration of a three-decade-old franchise a shot in the arm.

These aficionados self-identify as "bronies" (the word is a mashup of "bro" plus "ponies") and connect via conventions like BronyCon and websites like EquestriaDaily.com, an exhaustive repository of all things MLP-related. In response to posts about the upcoming events, some site users joked about wanting to bring younger relatives as a cover story for why they were playing with or buying the plush toys.

When the "Pinkie Pie" and "Rainbow Dash" stuffed ponies go on sale Monday, Build-A-Bear locations around the country are holding special events, for which fans are encouraged to dress to fit the theme. (For many customers, this probably means My Little Pony T-shirts, although some BronyCon attendees take it a step further and actually dress like the equine characters.)

Build-A-Bear and Hasbro were smart to cultivate this unlikely fan base, said Russ Crupnick, senior vice president of industry analysis for the NPD Group. "It's hard to develop new franchises," he said. "Anything you can do to invigorate the classics and keep the classic franchises moving is certainly helpful."

Last year, sales of plush toys dropped by about 20 percent, Crupnick said, so expanding its product offerings should be especially beneficial for Build-A-Bear.

There's a strong vein of nostalgia in toy markets today, which Hasbro has tapped into by growing its roster of pony merchandise. "While we will always market our brand for young girls, we've found ways to strike the right balance by working with licensees to offer our adult fans exciting merchandise geared just for them," Julie Duffy, Hasbro's vice president of global brand publicity, said in a statement. To that end, the company partnered with licensees that make everything from My Little Pony trading cards to comic books to USB drives.

On a conference call in November, Gerrick Johnson, equity research analyst at BMO Capital Markets, said retro toys like Teenage Mutant Ninja Turtles and Furby were poised to be popular for the holiday season.

"It's one of the things we saw very much at the toy fair in New York this year," said Stacy Leistner, spokesperson at the Toy Industry Association. "There were so many retro toys. ... In the case of My Little Pony, everything we're hearing and seeing about the adult fan base is that they've just gone crazy with the art, the colors, the design." The My Little Pony: Friendship is Magic cartoon series from which the new plush characters are drawn is designed to appeal to parents as well to kids with grown-up nods to pop culture.

"To the extent that you can broaden your user [base], it's just a strategy that makes sense as birth rates are down, the economy is still tight ... and there's increased competition from devices," Crupnick said. "Hasbro has been one of the companies on the cutting edge" of integrating elements like social media and mobile apps into traditional toys, he said.